feat: return workshop metadata with mod details

Include the Workshop title and preview image in the items response so the mod header survives a page refresh, not just navigation from search. Resolve both from the same Steam API call.

packages/shared/src/types.ts

@@ -87,6 +87,14 @@ export interface TTSMod {
   ObjectStates: TTSObject[];
 }
 
+/** A parsed save plus its Workshop metadata, returned by `GET /items/:id`. */
+export interface ModDetails {
+  mod: TTSMod;
+  /** Present when the metadata could be resolved via the Steam API. */
+  title?: string;
+  previewImageUrl?: string;
+}
+
 /** Metadata for a Workshop item, from the Steam Web API. */
 export interface WorkshopItem {
   id: string;